Chemical vapor deposition system cleaner

ABSTRACT

An apparatus for cleaning the interior surfaces of a vessel which includes a cleaning head supported and guided into the vessel by a rigid air shaft. The cleaning head is supplied with a process fluid and directs and removes the process fluid from a cleaning zone located on the interior surface of the vessel. The process fluid is heated by a heat exchanger hose assembly that is connected to the air shaft. The apparatus utilizes turbulent fluid flow, thermal shock, ultrasonic vibration and/or piezoelectric vibration to dislodge particulates from the inner surfaces of the vessel. The apparatus is useful for cleaning chemical vapor deposition reactors and other similar vessels.

This application is a divisional application of application Ser. No.07/574,155, filed Aug. 29, 1990, now U.S. Pat. No. 5,109,562, which is acontinuation-in-part application of application Ser. No. 07/400,920,filed Aug. 30, 1989, now abandoned.

TECHNICAL FIELD

This invention relates to methods and apparatus for cleaning theinterior surfaces of a chemical reactor and more particularly relates tomethods and apparatus for cleaning the interior surfaces of a chemicalvapor deposition reactor.

BACKGROUND ART

Surface contamination has become a major focus of research in thesemiconductor manufacturing industry. The effects caused by differentsources of surface contamination are responsible for most of the yieldloss currently experienced. Particulate contamination has beenidentified as one of the prime contributors to yield loss in advancedintegrated circuit (IC) fabrication.

The production process used to fabricate most integrated circuits useschemical vapor deposition (CVD) several times, in order to producecertain layers required for proper functioning of the circuit. DuringCVD, different gases are burned inside a furnace, and their combustionproduct (a glass in vapor form) is condensed onto the surface of thewafer as well as on to other surfaces within the furnace reactor. Whenthe process is complete and the wafers are withdrawn from the reactor,the thermal shock caused by the cooler air in the reactor furnace causesglass frost (vapox) formed on the inside surfaces of the reactionfurnace to crack and become loose.

The loosened vapox particles drop onto the surfaces of the waferssubsequently processed as a source of particulate contaminants causingsignificant reductions in final product yield. 50 to 70% of the failuresof integrated circuits are believed to be caused by contamination. Manythese failures are believed to be caused from contamination by these CVDparticulates. Because of this, furnaces are ideally cleaned after eachcritical process step and as often as possible for less criticalprocesses.

A typical cleaning requires shutting down the furnace, removing all thegas lines, sensors, and heaters, removing the furnace liner from insidethe furnace, soaking and scrubbing the liner with hydrofluoric acid,repairing the damage caused by the acid, replacing the liner in thefurnace, connecting all gas lines, sensors and heaters, testing andrecalibrating the furnace. A complete furnace cleaning can take from 12to 72 hours and must be done by highly trained technical personnel.Furnaces being cleaned are not processing products, causinginterruptions and disturbing the product flow throughout the facility.

While technology has focused on and advanced in the area of integratedcircuit manufacturing processes there remains a need in the industry fora convenient, efficient and economical method for cleaning chemicalvapor deposition reactors. Such a method would advantageously decreasethe yield loss currently experienced and would be highly desirable andaccepted by the industry.

DISCLOSURE OF THE INVENTION

It is accordingly one object of the present invention to provide anapparatus for cleaning the interior surfaces of a reactor.

It is another object of the present invention to provide an apparatusfor cleaning the interior surfaces of a chemical vapor depositionreactor furnace which does not require expensive dismantling of thereactor furnace nor a long term shut down of the chemical vapordeposition process.

It is a further object of the present invention to provide an apparatusfor cleaning the interior surfaces of a reactor which includes novelmeans to dislodge and remove particulates from the inner surfaces of thereactor.

A still further object of the present invention is to provide a methodfor cleaning the interior surfaces of a reactor by which particulatesformed on the interior surfaces of the reactor are dislodged and removedin a time efficient manner.

An even still further object of the present invention is to provide amethod for cleaning the interior surfaces of a chemical vapor depositionreactor furnace in which particulates formed on the interior surfaces ofthe reactor are dislodged by novel mechanical means and removed bysupplying and removing process fluids to and from the reactor.

According to the present invention there is provided an apparatus forcleaning the interior surfaces of a reactor which includes a cleaninghead which is supported by an air shaft. The cleaning head is designedto enter the interior of the reactor and direct processing fluids tocleaning zones defined by the cleaning head. The cleaning head furtherincludes means to produce mechanical dislodging forces to particulatesformed on the interior surfaces of the reactor. The processing fluidentrains particulates removed from the interior surfaces of the reactorand is exhausted through the cleaning head. Heat is exchanged betweenthe process fluid entering and leaving the reactor by means of bothrigid and flexible heat exchanger hose assemblies so as to controlthermal shock during the cleaning operation.

The present invention further provides for a method of cleaning theinterior surfaces of a reactor which utilizes a novel apparatusdescribed above.

BRIEF DESCRIPTION OF DRAWINGS

The present invention will now be described with reference to theannexed drawings, which are given by way of non-limiting examples onlyin which:

FIG. 1 is a schematic cross-sectional view of the overall apparatusaccording to one embodiment of the present invention.

FIG. 2 is a partially schematic cross-sectional view of the cleaninghead, air shaft and heat exchanger hose assembly according to oneembodiment of the present invention.

FIG. 3 is a cross-sectional view of a portion of the heat exchanger hoseassembly which illustrates one embodiment of the process fluid supplyand removal hoses.

FIG. 4 is a partially schematic cross-sectional view of the processfluid control section used in conjunction with the cleaning system ofthe present invention.

FIG. 5 ia a schematic cross-sectional view illustrating an alternativeembodiment of the present invention wherein process fluid is fed intothe system at a location between the air shaft and the heat exchangerhose assembly.

BEST MODE FOR CARRYING OUT THE INVENTION

The present invention relates to a cleaning system which can be utilizedto clean the interior surfaces of a wide variety of chemical reactorsand furnaces. In particular, the present invention was designed forcleaning the interior surfaces of chemical vapor deposition reactorfurnaces wherein particulates formed during chemical vapor depositionprocesses are removed by the present invention. However, it is notedthat the present invention is not limited for use in connection withchemical vapor deposition reactor furnaces but can be used to clean theinterior surfaces of various chemical reactors and other similar vesselsand containers. Such reactors and other vessels may have a variety ofcross-sectional shapes such as circular, square, rectangular, etc. Inorder to accommodate reactors of different cross-sectional shapes, theshape of the cleaning head should be complementarily shaped to fit theparticular reactor or vessel interior to be cleaned.

The basic components of the present invention, as will be discussed indetail below, include a cleaning head which is insertable into thereactor and means for supplying and removing process fluid to and fromthe reactor through the cleaning head. The cleaning head includes meansto distribute and direct the incoming process fluid to a cleaning zonedefined adjacent the cleaning head and further includes exhaust portsfor removing process fluid from the interior of the reactor. Inoperation, the entering process fluid is directed to a portion of theinterior surface of the reactor located within the defined cleaning zoneand dislodges and removes particulate matter from the interior surface.The dislodged particulate matter becomes entrained in the process fluidand is removed together with the process fluid through exhaust portslocated in the cleaning head.

To assist the removal of the particulate matter by the flowing processfluid the cleaning head may be equipped with additional mechanicaldislodging means, such as an ultrasonic or piezoelectric vibrator, whichaids in dislodging the particulate matter from the interior surfaces ofthe reactor. In a further embodiment the incoming process fluid may bethermally cycled so as to effect a thermal shock to the particulatematter thereby aiding in dislodging the particulate matter.

In order to adapt the present invention to be utilized in conjunctionwith heated reactors the incoming process fluid is heated so as tocontrol and avoid excessive thermal shock within the reactor. Whilethermal shock may be used to dislodge particulate matter, excessivethermal shock may damage the reactor structure. The heating of theincoming process fluid is accomplished by providing both rigid andflexible heat exchanger hose assemblies having an outer process fluidsupply hose and one or more inner process fluid removal hoses which arelocated within the outer process fluid supply hose. In this arrangement,heat is transferred from the process fluid removed from the reactor andis transferred to the process fluid entering the reactor. In a preferredembodiment, as discussed in detail below, the process fluid removalhoses are spirally positioned within the process fluid supply hose tocause turbulent flow of the process fluid and thereby effect a greaterheat exchange rate and contribute to the turbulence of the fluid as itis distributed from the cleaning head to thereby aid in dislodgingparticulate matter from the interior surface of the reactor.

The afore-mentioned heat exchanger hose assembly is flexible. Incontrast, the air shaft which connects between the flexible heatexchanger hose assembly and the cleaning head is made of rigid tubularassemblies comprising an outer process fluid supply tube and an innerprocess fluid removal tube. Being rigid, the air shaft may be supportedin a suitable guide means for directing the cleaning head into thereactor. This support means, in a preferred embodiment is furtherdesigned to fit over an opening in the reactor in a sealingly tight fit,whereby the overall system can be operated under a negative pressure toinsure that all contaminants or particulates are confined and removed bythe cleaning system.

The particulate matter entrained in the process fluid is removed fromthe removed process fluid by a suitable separation means which, in apreferred embodiment, includes a liquid filter through which theprocessed fluids, i.e., gases are bubbled. The removed process fluidafter passing through the filtration means may be released into theenvironment thereafter or recycled back into the system. In a preferredembodiment the process fluid may include either ambient atmosphere or aninert gas such as nitrogen gas. In further embodiments, the processfluid may be liquid fluid and the filtration means may be any suitablemeans for removing solid particulates or contaminates from the liquidprocess fluid.

FIG. 1 illustrates one embodiment of the present invention. In FIG. 1cleaner head 2 is shown inserted into reactor 1. Cleaner head 2 issupported by air shaft 3 which passes through and is guided by cover 4which serves as an air lock for sealing reactor 1 so that the cleaningoperation may be operated under an overall negative pressure. Air shaft3 is connected to heat exchanger hose assembly 5 which comprisesflexible hoses for supplying and removing process fluid to and from theinterior of the reactor 1. Heat exchanger hose assembly 5 is connectedto a process fluid control section 6 which includes valve 7 which admitsprocess fluid through port 8 into a process fluid supply hose located inheat exchanger hose assembly 5. The process fluid removed from reactor 1is directed by means of valve 7 through filter means 9. In operation,the overall system is maintained under a negative pressure by vacuumgenerator 10 located within the fluid control section 6. Spent processfluid, after having entrained particulates removed therefrom isexhausted through exhaust port 11.

FIG. 2 is a partially schematic cross-sectional view of one embodimentof the apparatus according to the present invention which illustratesmore specific features of the apparatus. As seen in FIG. 2, cleaninghead 2 includes inlet ports 12 through which entering process fluidsenter the interior of the reactor and exhaust ports 13 through whichprocess fluids are removed from the interior of the reactor. Theentering process fluids pass through inlet ports 12 and are directed tothe peripheral surfaces of the cleaning head by means of a fluiddistributor 14. The fluids flow radially outward from the center of thefluid cleaning head towards the adjacent interior surfaces of thereactor and radially inward to the exhaust ports. The highly turbulentfluid contacts a small area of the interior surface of the reactor whichdefines the cleaning zone 15.

To aid in dislodging particulate matter from the interior surface of thereactor, the peripheral portions of the cleaning head are equipped withbrush elements 16 as illustrated in FIG. 2. In a preferred embodiment,illustrated in FIG. 2, several brush elements are arranged on eitherside of the cleaning head to define cleaning zone 15 therebetween. Thebrush elements 16 and fluid distributor 14 are preferably made ofmaterials which will not contaminate the surface being cleaned. Suitablematerials from which to make the brush elements and flow distributorinclude inert materials, materials virtually identical with thesubstrate material of the surface being cleaned, e.g., the brushelements may be made from silica fibers when cleaning a silica reactortube, and materials physically incapable of prolonged contact with thesubstrate material of the surface being cleaned under conditions ofnormal operation of the device being cleaned, e.g., the materials may bepolyamide when cleaning a silica reactor tube, so that any materialremaining within the tube after cleaning are abated by or chemicallydecomposed upon contact with the tube substrate at operationaltemperatures.

As a further aid for dislodging particulate matter from the interiorsurfaces of the reactor cleaning head is equipped with a means 24 foreffecting mechanical action on the cleaning head which may be locatedwithin the interior of the fluid distributor in a more preferredembodiment. Such mechanical means may include an ultrasonic vibrator ora piezoelectric vibrator whose vibration is transferred from thecleaning head via the brush elements to the interior surface of thereactor so as to aid in dislodging particulate matter from the interiorsurfaces of the reactor. The cleaning head as illustrated should besuitably sized for the particular reactor so that there is anappropriate area between the peripheral surfaces of the cleaning headand the interior surfaces of the reactor. As illustrated, the brushelements may be positioned to extend between the cleaning and contactthe interior surface of the reactor so that they can be used to applymechanical force to the particulate matter on the interior surfaces. Inaddition to removing particulate matter from the interior surfaces ofthe reactor, the exhausted process fluid also removes particulates andother contaminants that are freely suspended within the reactorinterior.

Cleaning head is attached as illustrated to air shaft 3 which may besupported and guided by means of cover or air lock 4 or other suitablemeans. This cover serves as an air lock in that it is sealingly attachedto the reactor so that the reactor and the entire system can bemaintained under a negative pressure during operation so as to ensurecontainment of all particulate matter within the reactor. In thisregard, it is recognized that in certain reactors, particularly chemicalvapor deposition and nuclear reactors, exposure to particulates built upwithin the reactor can cause serious health problems to workers exposedto these particulates. As illustrated in FIG. 2 the cover or air lockmay optionally include a containment zone 18 of a suitable volume forcontaining cleaning head before and after it is positioned within thereactor.

The air shaft, as illustrated in the cross-sectional view, includes twoor more rigid collinear tubular members 19 and 20. The annular spacebetween the tubular members defines an annular passageway in whichprocess fluid may be supplied to the cleaning head. The interior tubularmember 19 defines a conduit through which the contaminated process fluidor the process fluid having the dislodged particulates entrained thereinis removed from the cleaning head. The annular passageway is connectedto the process fluid inlet port of the cleaning head and the processfluid removal conduit is connected to the exhaust ports in the cleaninghead.

The air shaft as illustrated in FIG. 2 is connected to the heatexchanger hose assembly by an optional filter and heating unit 21located along or between the air shaft 3 and heat exchanger hoseassembly 5 as illustrated in FIG. 2. This optional filter and heatingunit is utilized to properly condition the process fluid as it entersthe air shaft and subsequently enters the interior of the reactor. Instart up operations the heater unit may be operated by a suitablecontrol means 21a to heat incoming process fluid, until removed processfluid is at a temperature comparable to that experienced during thesubsequent process cycle. The heater may also be utilized to thermallycycle incoming process fluid in order to assist in dislodgingparticulates as discussed above. The filter unit is particularlyutilized for removing entrained contaminant particulates from theprocess fluid prior to its entry into the vessel. To provide informationrequired to effectively control and operate the invention, varioussensor devices may be located and used in appropriate locationsthroughout the system. For illustrative purposes, one set of suchsensors, e.g. thermocouple and photoelectric particle detector, element17 is located adjacent the cleaning head as illustrated as in FIG. 2.

FIG. 3 illustrates a cross-sectional view of the heat exchanger hoseassembly. As illustrated in FIG. 3 the heat exchanger hose assembly 5includes an outer process fluid supply hose 22 and one or more innerprocess fluid removal hoses 23. In a preferred embodiment as illustratedin FIG. 3, two inner process fluid removal hoses are positioned in theouter process fluid supply hose in a spiralling arrangement. Thispreferred spiralling arrangement in the process fluid removal hosesincreases the turbulent action of the process fluid as it is supplied toand removed from the heat exchanger hose assembly, thus aiding the heattransfer between the exiting heated process fluid and the enteringcooler process fluid. The heat exchanger hose assembly is made flexibleso as to be easily manipulated as the cleaning head is passed in and outof the reactor.

FIG. 4 schematically illustrates the elements of the fluid controlsection 6. As illustrated in FIG. 4 the heat exchanger hose assemblyconnects to valve 7 which directs process fluid into and out of theappropriate hoses of the heat exchanger hose assembly. The processfluid, which may comprise ambient air is fed through entry port 8 andvalve 7 into the heat exchanger hose assembly. Exiting process fluid isreceived from the heat exchanger hose assembly, is passed through valve7 and is directed into a filtration means 9. This filtration means maycomprise any suitable filtration means for removing the particulatematerial from the process fluid. Depending on the nature of the processfluid, i.e., liquid or gas, any suitable filtration means may beselected, e.g. physical, chemical, etc. In a preferred embodimentparticulate materials from a chemical vapor deposition reactor werefiltered by bubbling the exhausted process gas through a cooled liquid.Clean or purified removed process fluid is passed from the filteringsystem through an exhaust port 11 which may release the fluid into theambient atmosphere or direct the fluid to other fluid handling orcontainment means.

As illustrated in FIG. 4 the system is connected to a vacuum generator10 which maintains an overall negative pressure throughout the entiresystem during operation. By operating under a vacuum all particulatesare necessarily collected, contained and processed through the cleaningsystem.

In operation, the cleaning system is attached to an opening in thereactor such as an access opening by means of the air lock or coverwhich provides for a virtually fluid tight seal between the cleaningsystem and the reactor. Once attached to the reactor, the cleaning headis passed into and through the interior of the reactor so that the brushelements contact the inner surfaces of the reactor. The cleaning head isguided as it passes through the reactor by means of the air lock orcover which includes sufficient structure to support the air shaft andthereby guide the movement of the cleaning head. Alternatively, thecleaning head may be guided by suitable rollers or cantilever assembliesconnected to the cleaning head.

As the cleaning head is passed through the reactor the fluid controlsection is activated so that the vacuum generator creates an overallnegative pressure throughout both the reactor and the cleaning system.As a result of this negative pressure processing fluids, such as ambientatmosphere enters entry port 8 of the fluid control section and arepassed by means of valve 7 through the heat exchanger hose assembly, theoptional heating element, the prechamber filter unit, and the air shaftto be distributed by means of the cleaning head against the interiorsurfaces of the reactor.

As the cleaning head is passed into and through the reactor, thecleaning head may be subject to any desired combination of linear,vibrational and rotational motion. The vibrational motion is provided bythe mechanical means 24 described above. The linear and rotationalmotion may be provided either manually or by a suitable mechanical meansas the connected air shaft 3 is guided though cover or air lock 4.

After contacting the interior surfaces of the reactor and dislodging,entraining and removing particulate matter from the interior surface ofthe reactor, the processing fluid becomes heated due to the temperatureof the reactor and is removed through the exhaust port in the cleaninghead and passes through the air shaft and enters the heat exchanger hoseassembly. As the heated process fluid is removed through the heatexchanger hose assembly heat is exchanged between the removed processfluid and transferred into the entering or supplied process fluid.Additional heat, as required, and particularly upon start up operationis added by means of the filtering and heating unit. As the exhausted orremoved processing fluid enters the fluid control section processingfluid entrained with removed particulates is directed by means of valve7 to filtering means 9 wherein the particulate material is removed fromthe processing fluid.

In a preferred embodiment the particulates are removed as a result ofbubbling the process fluid through a cooled liquid. These removedparticulates may be retained for later analysis and monitoring of theparticular reaction occurring in the reactor unit. The purifiedprocessing fluid, having the particulates removed therefrom, isexhausted through exhaust port 11.

In an alternative embodiment of the present invention as illustrated inFIG. 5, incoming process fluid may be introduced into the system at oneor more locations between the air shaft and the heat exchanger hoseassembly in lieu of the process fluid entry port 8. In this manner,thermal or flow velocity characteristics of the process may be changedso as to control the surface temperature of the heat exchanger hoseassembly.

As illustrated in FIG. 5, valve 7 and process fluid entry port 8 areremoved from the fluid control section 6 and a valve assembly 7' ofknown type, which includes a process fluid entry port 8', is positionedbetween air shaft 3 and heat exchanger hose assembly 5. In theembodiment of FIG. 5 valve 7 has further been replaced with a couplingconnector 25 which connects the outer process fluid supply hose and theinner process fluid removal hoses to single fluid conduit 26.

In operation of the embodiment of the invention illustrated in FIG. 5processing fluid, e.g., ambient atmosphere, enters process fluid entryport 8' and is distributed by valve assembly 7' in three portions. Aminor portion, e.g., 5-15 vol. % of the entering process fluid isdirected by valve assembly 7' to flow down the outer process fluidsupply hose 22 to combine with the balance of the process fluid atcoupling connector 25. A second, major portion, e.g., 70-90 vol. % ofthe entering process fluid is directed by valve assembly 7' to flowthrough the exterior tubular member 20 of air shaft 3 into the cleaningzone and then through the interior tubular member 19 of air shaft 3 tovalve assembly 7'. A further, minor portion, e.g., 5-15 vol. % of theentering process fluid enters process fluid entry port 8' and iscombined by the valve assembly with the major portion of the processfluid flowing down the outer process fluid supply hose 22. The combinedmajor and minor portion of the process fluid flows from the valveassembly 7' through the inner process fluid hoses 23 to combine with thebalance of the process fluid at coupling connector 25. Thereafter, theprocess fluid is filtered in the fluid control section as describedabove.

As described above, in the embodiment of the invention illustrated inFIG. 5, all of the process fluid enters process fluid entry port 8'.Therefore, as described, the process fluid flows in one direction,towards the process fluid control section 6, in heat exchanger hoseassembly. The advantage provided by the embodiment of the inventionillustrated in FIG. 5 is that surface temperature of the heat exchangerhose assembly can be lowered and controlled by combining hot and ambientprocess fluid within the heat exchanger hose assembly.

The cleaning system of the present invention provides for a convenient,efficient and economical manner of cleaning the interior surfaces of areactor or similar vessel. As applied to chemical vapor depositionprocesses, the present invention could be used to clean chemical vapordeposition reactor furnaces in a very short time period without the needof highly trained technical operators. The present invention canincrease furnace availability, free technicians to perform othercritical duties and increase process control, product yield and devicereliability.

While the cleaning system of the present invention has been described inthe particular context for cleaning the interior surfaces of vessels,there are more particular features and further embodiments which areapplicable to several diverse applications. For example, the abovedescription describes the use of a set of sensors for monitoring andcontrolling the cleaning operation which includes a thermocouple and aphotoelectric particle detector. It is sufficient to note that,depending upon the particular application, the number and types ofsensors, e.g., thermocouples, thermometers, spectrum analyzers and thelike; gas component analyzers; fluid pressure and flow sensors, e.g.,manometers, pilot tubes, anemometers, mass flow sensors, bourdon tubegages, differential pressure gauges, flow meters, diaphragm gauges andthe like; particulate sensors, e.g, photoelectric analyzers, impactanalyzers, mass analyzers, doppler shift analyzers, ultrasonicanalyzers, conductivity analyzers, electric field analyzers and thelike; clearance sensors (to measure the gap between the brush elementsand the surface to be treated), e.g., frequency analyzers, transducers,reflectance meters, resonance analyzers, electromagnetic fieldanalyzers, fiber strain analyzers, differential pressure analyzers andthe like; and heat flow sensors, e.g., differential pyrometers, poweruse analyzers, strain sensors, chronometric analyzers and the like maybe appropriately selected for the particular parameters, properties orcomponents to be mounted for control purposes.

The positioning of the various sensor devices is dependent on theparameter property or components to be monitored and controlled. Forexample a thermocouple and/or anemometer may be located in the processfluid intake chamber. Other thermocouples may be located in the heatingand final filter unit entrance and exit. Another thermocouple andphotoelectric particle detector may be located at the entrance to theexhaust section on the rigid heat exchanger. Another thermocouple may belocated at the entrance to the bubble filtration tank. A differentialmanometer may be located across the entrance and exit ports for theprocess fluid lines. Each of these sensor locations and means wouldprovide for the particular sensing and control of specific portions ofthe cleaning system.

It has been discovered that minor modifications to the cleaning headassembly and airlock enable the airlock unit to complete the boundariesenclosing the cleaning zone which are not provided by the surface beingcleaned. With such modification, irregular and/or unbounded surfaces canbe cleaned by the present invention. For example, the area betweencooling fins on a heat exchanger within a nuclear reactor can easily becleaned by a simple modification of the cleaning head. Similarly, thefloor of an emergency room of a hospital can be effectively cleaned andsterilized by a cleaning head modified to provide a bounded treatingsurface.

While the system of the present invention is primarily designed forcleaning surfaces, suitable processing fluids can be used to chemicallytreat, sterilize, alter and coat desired surfaces. The addition ofultraviolet and/or infrared and/or microwave and/or x-ray and/or nuclearradiation sources to the surface to be treated will provide anenvironment lethal to lifeforms, enabling the surface to be safelycleaned without exposure of the operator to harmful sterilizing agentsor the lifeforms being exterminated. Exposure to nuclear ionizing ortransmuting radiation would be applicable to decompose surfaces such ascross-linked polymers.

Control and magnification of the amplitude of the thermal, ultrasonic,and piezoelectric stress induction mechanics will enable disruption andremoval of surface material immediately adjacent to the treatment orcleaning zone from identical substrate material out of the range ofeffective disruption, resulting in additional application of theinvention as a mining, boring and/or tunneling tool and as a surfaceremover.

Appropriate application of stress induction techniques effective uponthe surface layer but less effective upon an adjacent non-identicalsubstrate will allow the device to dislodge and remove such surfacelayers without damage to the underlying substrate. For example,appropriate selection of ultrasonic frequencies would allow removal ofice from sidewalks without melting or scraping. Likewise, appropriateselection of ultrasonic, electromagnetic radiation frequencies andprocess fluids would dislodge and decompose asbestos fibers and bindermaterials from surfaces in a safe and effective manner.

Thus the system of the present invention has usefulness for altering thetopology, chemical identity, or physical properties of surfaces.

Although the invention has been described with reference to particularmeans, materials and embodiments, from the foregoing description, oneskilled in the art can ascertain the essential characteristics of thepresent invention and various changes and modifications may be made toadapt the various uses and characteristics thereof without departingfrom the spirit and scope of the present invention as described in theclaims that follow.

I claim:
 1. A method of cleaning the interior surfaces of a vessel whichcomprises:providing a cleaning head having at least two spaced apartbrush elements which are substantially perpendicular to an interiorsurface of a vessel; positioning said cleaning head in said vessel;defining a cleaning zone between said at least two spaced apart brushelements and between said interior surface of said vessel; dislodgingparticulates from the interior surface of said vessel; and removing saiddislodged particulates, said dislodging being accomplished by supplyinga heated turbulent process fluid into said defined cleaning zone in saidvessel and by further subjecting said particulates to a process selectedfrom the group consisting of mechanical agitation, thermal stress,physical interaction with said process fluid, chemical interaction withsaid process fluid and combinations thereof.
 2. A method of cleaning theinterior surfaces of a vessel according to claim 1, wherein saiddislodged particles are removed from said vessel by entraining dislodgedparticulates into said supplied process fluid and exhausting saidsupplied process fluid along with said dislodged particulates.
 3. Amethod of cleaning the interior surfaces of a vessel according to claim2, wherein said process fluid is both supplied to and removed from saidvessel and thermal energy is exchanged between said process fluid thatis removed from said vessel and said process fluid that is supplied tosaid vessel so as to equalize the temperature of said process fluidsupplied to said vessel with that removed from said vessel.
 4. A methodof cleaning the interior surfaces of a vessel according to claim 1,wherein said removed particulates are collected after being removed fromsaid vessel.
 5. A method of cleaning the interior surfaces of a vesselaccording to claim 1, wherein said interior of said vessel is subjectedto a negatived pressure during said cleaning.
 6. A method for cleaningthe interior surfaces of a vessel according to claim 1, wherein saidvessel comprises a reactor.
 7. A method for cleaning the interiorsurfaces of a vessel according to claim 1, wherein said reactorcomprises a chemical vapor deposition reactor.
 8. A method for cleaningthe interior surfaces of a vessel according to claim 1, wherein saidprocess fluid is selected from the group consisting of inert gases andambient atmosphere.
 9. A method of cleaning the interior surfaces of avessel according to claim 1, wherein said mechanical agitation consistsof ultrasonic vibration or piezoelectric vibration.